Field of the Invention
The embodiments disclosed herein relate generally to 3-D image generation and the identification and tracking of objects, and more particularly to LADAR sensors for mobile applications such as road hazard avoidance, collision avoidance, and autonomous navigation. The invention compensates for the issues arising from the operation of a ladar sensor having a limited optical power output.
References to Related Art
The 3-D imaging technology disclosed in Stettner et al, U.S. Pat. Nos. 5,446,529, 6,133,989 and 6,414,746 provides with a single pulse of light, typically pulsed laser light, all the information of a conventional 2-D picture along with the third dimensional coordinates; it furnishes the 3-D coordinates of everything in its field of view. This use is typically referred to as flash 3-D imaging in analogy with ordinary digital 2-D cameras using flash attachments for a self contained source of light. As with ordinary 2-D digital cameras, the light is focused by a lens on the focal plane of the LADAR sensor, which contains an array of pixels called a focal plane array (FPA). In the case of a LADAR sensor these pixels are “smart” and can collect data which enables a processor to calculate the round-trip time of flight of the laser pulse to reflective features on the object of interest.
Many systems have been proposed to meet the challenge of using optical imaging and video cameras in a vehicle system to create 3-D maps of scenes and models of solid objects, and to use the 3-D database to navigate, steer, and avoid collisions with stationary or moving objects. Stereo systems, holographic capture systems, and those which acquire shape from motion, have not been able to demonstrate adequate performance in this application, but 3D LADAR based systems have shown the ability to rapidly capture 3-D images of objects and roadway features in the path of a moving vehicle, or travelling on an intersecting path, with sufficient speed and accuracy to allow the host vehicle to avoid collisions and road hazards, and steer the best path. In order to produce a low cost and rugged design, it is foreseeable there will be a need to use a semiconductor type laser pulse transmitter having a limited optical output power.
It is therefore desirable to provide a LADAR sensor capable of operating with a low power semiconductor laser array to illuminate the field of view of the LADAR sensor. It is further desirable that the LADAR sensor is capable of mapping the entire area surrounding the vehicle, and allows for the avoidance of other moving vehicles, road hazards, and pedestrians.